A prevalent isotopic signature in the East African upper mantle: implications for the composition of the African LLSVP
Abstract
The recognition of an association between thermo-chemical anomalies extending into the upper mantle and the Pacific and African Large Low Velocity Shear Provinces (LLSVPs), provides an opportunity to probe the potential composition of these large-scale mantle features. While ocean islands provide a relatively direct probe of the Pacific LLSVP, the majority of magmatism associated with the African LLSVP erupts through continental lithosphere. A recent synthesis of data collated from the East African Rift provides the most complete probe into magmatism within this region and reveals the pervasive overprint of the continental lithosphere on rift lavas. This lithospheric overprint may take the form of assimilation of continental crust during melt evolution, melt generation from metasomes located within the continental lithospheric mantle, or detachment and mixing of lithosphere into the ambient upper mantle. Unsurprisingly, regions of the East African rift that are in proximity to cratonic lithosphere exhibit the most exotic isotopic signatures; regions traversing more recently formed lithosphere show less isotopic variability. When interpreted collectively, it is evident that these diverse lithospheric isotopic domains represent distinct endmembers that are defined by the arrays formed by East African Rift lavas. Critically, these arrays converge on a single composition correlative to the Afar Mantle Plume, with the implication that this material is present throughout the East African Upper mantle. Accordingly, I suggest that the prevalent composition of material rising from the African LLSVP is equivalent to that of the Afar Mantle plume.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMT007...09R
- Keywords:
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- 7209 Earthquake dynamics;
- SEISMOLOGY;
- 7280 Volcano seismology;
- SEISMOLOGY;
- 8105 Continental margins: divergent;
- TECTONOPHYSICS;
- 8413 Subduction zone processes;
- VOLCANOLOGY